Immunosuppressive Properties of α1‐Microglobulin

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Abstract
α1-Microglobulin (α1m), a serum glycoprotein (26,000 d). was found to impede the proliferative response of human lymphocytes to purified protein derivative (PPD) and tetanus toxoid. The data suggest that, α1m operates through an unstable suppressor mechanism, which no longer can function after 24 h of preculturing. This effect of α1m on antigen stimulation did not seem to be due to binding of α1m to PPD or cells, to altered kinetics of the PPD response, or to non-specific cytotoxicity. In contrast, PPD-induced leucocyte migration inhibition was not reversed by α1m. α1m did not cause significant inhibition in experiments in which lymphocytes were stimulated by the mitogens phytohaemagglutinin or concanavalin A. Finally, α1m had its own leucocyte migration inhibitory effect.